body {  
  opacity: 0;
  visibility: hidden;
   -webkit-transition: all 0.1s linear;
  -moz-transition: all 0.1s linear;
  -ms-transition: all 0.1s linear;
  -o-transition: all 0.1s linear;
  transition: all 0.1s linear;      
}

body.fadeIn {
  opacity: 1;
  visibility: visible;
}